Is there a role for dual PI3K/mTOR inhibitors for patients affected with lymphoma? Chiara Tarantelli 1, Antonio Lupia 2, Anastasios Stathis 3,4, Francesco Bertoni 1,3 1 Institute of Oncology Research, Faculty of Biomedical Sciences, USI, Bellinzona, Switzerland; 2 Department of Health Sciences, University "Magna Græcia" of Catanzaro, Catanzaro, Italy; 3, Oncology Institute of Southern Switzerland, Bellinzona, Switzerland; 4 Faculty of Biomedical Sciences, USI, Lugano, Switzerland. Supplementary Material Additional Dual PI3K/mTOR inhibitors We discuss here the dual PI3K/mTOR inhibitors with no available clinical data in patients with lymphoma. Dactolisib (BEZ235/NVP-BEZ235) is the most studied dual PI3K/mTOR inhibitor. It is a potent inhibitor of all the four PI3K isoforms (slightly less for the p110β), of TORC1/TORC2 and also of the PI3Kα mutants most commonly detected in solid tumors [1]. Dactolisib has preclinical anti-tumor activity in different models of B and T cell lymphomas [2-18]. The compound can also act as microtubule destabilizer [7] and it inhibits DNA damage response (DDR) kinases [12]. Indeed, Shortt and Coll. suggested that it is indeed the triple inhibition of PI3K, mTOR and DDR kinases playing a fundamental role in the higher activity seen with dactolisib in inducing apoptosis in Myc-driven mouse lymphoma models in comparison with single PI3K or mTOR inhibitors [12]. The clinical program for dactolisib has been stopped due to a high variable pharmacokinetic profile observed in the phase I studies [19]. Despite all the preclinical data available, to the best of our knowledge, no lymphoma patient has been treated with dactolisib. BGT226/NVP-BGT226 inhibits p110α, p110β, p110δ, and p110γ, with a preference for p110α (wild type and mutated), and TORC1/TORC2 [20]. Besides showing activity in solid tumors, acute leukemia and multiple myeloma models [20-23], the compound has shown preclinical anti-lymphoma activity [16, 24]. Without enrolling any lymphoma patient, a phase I study performed in USA and Europe led to a stop in the clinical development of BGT226 due to the inability of reaching concentrations expected to properly inhibit PI3K signaling in the absence of dose-limiting toxicity [25]. Similar toxicity was observed in a parallel phase I study performed in Japanese patients with solid tumors, which stopped before reaching the dose-limiting toxicity based on the already available of the other study [26]. Resistance to BEZ235 and BGT226 is associated to higher expression of PAK1 gene, and combination of PI3K inhibition and PAK1 inhibition is synergistic [16]. PI103 is a strong inhibitor of p110α, p110β, p110δ L, p110γ, TORC1/TORC2 and also of DNA-PK with preclinical anti-tumor activity in solid tumors [27, 28] and mouse and human T-cell lymphoma models [29-31]. Apitolisib (GDC0980/RG7422/apitolisib) is a potent inhibitor of all the PI3K and of TORC1/TORC2 with anti-tumor activity in different solid tumor cell lines [32, 33]. Apitolisib has also strong in vitro activity in B cell lymphoma cell lines [34]. No patient with lymphoma was enrolled in the phase I (NCT00854152) [35], and no information on recruited patients is available from a second study (NCT00854126) [36], already closed. PF04691502 inhibits the four PI3K isoforms, including mutant p110α, and TORC1/TORC2 and has preclinical activity in solid tumors [37], DLBCL, MCL [38] and cutaneous T cell lymphomas [39]. No study has been performed for patients with lymphoma. Omipalisib (GSK2126458/GSK458) is an inhibitor of p110α (wild type and mutant), p110β, p110δ, p110γ, TORC1 and TORC2 with activity in cell lines derived from solid tumors [40], from BL [41] and T cell lymphomas [42]. Omipalisib has not been clinically evaluated in patients with lymphoma. VS5584/SB2343 has shown activity in solid tumor, BL [43, 44] and MM cell lines [43]. No data are available of the phase I study (NCT01991938) that had already enrolled 75 patients and was terminated due to lack of recruitment and the company's decision to de-prioritize compound development. Finally, NU7441 is believed to mainly act as a DNA-PK inhibitor but it also targets PI3Ks and mTOR [45]. It has preclinical activity in cell lines derived from BL and from other lymphoma subtypes [46]. 1 To the best of our knowledge, there are no reported data of activity in lymphoma models using DS7423 [47], the GDC-0941 derivative GNE-477 [48], the PF-04691502 derivative PF-04979064 [49], PKI-179 [50], PKI-402 [51, 52], PQR530 [53], PWT33597 (VDC-597 currently commercialized as veterinary anticancer drug) [54], samotolisib (LY3023414) [55, 56], SN32976 [57, 58], WJD008 [59], and for the multitarget PI3K/mTOR/ALK-1/DNA-PK inhibitor Panulisib (P7170) [60-62]. References 1. Maira, S. M.; Stauffer, F.; Brueggen, J.; Furet, P.; Schnell, C.; Fritsch, C.; Brachmann, S.; Chene, P.; De Pover, A.; Schoemaker, K.; Fabbro, D.; Gabriel, D.; Simonen, M.; Murphy, L.; Finan, P.; Sellers, W.; Garcia-Echeverria, C., Identification and characterization of NVP-BEZ235, a new orally available dual phosphatidylinositol 3- kinase/mammalian target of rapamycin inhibitor with potent in vivo antitumor activity. Mol Cancer Ther 2008, 7, (7), 1851-63. 2. Aust, M.; Wallace, L.; Grant, S., Inhibition Of PI3K/mTOR By BEZ235 Dramatically Potentiates Panobinostat- Induced Lethality In Diffuse Large B-Cell Lymphoma Through Multiple Mechanisms. Blood 2013, 122, (21), 817- 817. 3. Rahmani, M.; Aust, M. M.; Benson, E. C.; Wallace, L.; Friedberg, J.; Grant, S., PI3K/mTOR inhibition markedly potentiates HDAC inhibitor activity in NHL cells through BIM- and MCL-1-dependent mechanisms in vitro and in vivo. Clinical cancer research : an official journal of the American Association for Cancer Research 2014, 20, (18), 4849-60. 4. Buglio, D.; Lemoine, M.; Neelapu, S. S.; Vega, F.; Berry, D.; Younes, A., NVP-BEZ235, A Dual Inhibitor of Phosphoinositol-3-Kinase (PI3K) and Mammalian Target of Rapamycin (mTOR), Is a Potent Inhibitor of Lymphoma Cell Growth and Survival. Blood 2011, 118, (21), 4965-4965. 5. Bhende, P. M.; Park, S. I.; Lim, M. S.; Dittmer, D. P.; Damania, B., The dual PI3K/mTOR inhibitor, NVP-BEZ235, is efficacious against follicular lymphoma. Leukemia 2010, 24, (10), 1781-4. 6. Kim, A.; Park, S.; Lee, J. E.; Jang, W. S.; Lee, S. J.; Kang, H. J.; Lee, S. S., The dual PI3K and mTOR inhibitor NVP-BEZ235 exhibits anti-proliferative activity and overcomes bortezomib resistance in mantle cell lymphoma cells. Leukemia research 2012, 36, (7), 912-20. 7. Civallero, M.; CosenZa, M.; PoZZi, S.; Bari, A.; Ferri, P.; Sacchi, S., Activity of BKM120 and BEZ235 against Lymphoma Cells. BioMed Research International 2015, 2015, 870918. 8. Anders, P.; Bhende, P. M.; Foote, M.; Dittmer, D. P.; Park, S. I.; Damania, B., Dual inhibition of phosphatidylinositol 3-kinase/mammalian target of rapamycin and mitogen activated protein kinase pathways in non-Hodgkin lymphoma. Leukemia & lymphoma 2015, 56, (1), 263-6. 9. Vergaro, V.; Civallero, M.; Citti, C.; CosenZa, M.; Baldassarre, F.; Cannazza, G.; Pozzi, S.; Sacchi, S.; Fanizzi, F. P.; Ciccarella, G., Cell-Penetrating CaCO(3) Nanocrystals for Improved Transport of NVP-BEZ235 across Membrane Barrier in T-Cell Lymphoma. Cancers (Basel) 2018, 10, (2), 31. 10. Choudhary, G. S.; Al-Harbi, S.; MaZumder, S.; Hill, B. T.; Smith, M. R.; Bodo, J.; Hsi, E. D.; Almasan, A., MCL-1 and BCL-xL-dependent resistance to the BCL-2 inhibitor ABT-199 can be overcome by preventing PI3K/AKT/mTOR activation in lymphoid malignancies. Cell Death Dis 2015, 6, (e1593), e1593. 11. Civallero, M.; CosenZa, M.; Marcheselli, L.; PoZZi, S.; Sacchi, S., NVP-BEZ235 alone and in combination in mantle cell lymphoma: an effective therapeutic strategy. Expert opinion on investigational drugs 2012, 21, (11), 1597-606. 12. Shortt, J.; Martin, B. P.; Newbold, A.; Hannan, K. M.; Devlin, J. R.; Baker, A. J.; Ralli, R.; Cullinane, C.; Schmitt, C. A.; Reimann, M.; Hall, M. N.; Wall, M.; Hannan, R. D.; Pearson, R. B.; McArthur, G. A.; Johnstone, R. W., Combined inhibition of PI3K-related DNA damage response kinases and mTORC1 induces apoptosis in MYC-driven B-cell lymphomas. Blood 2013, 121, (15), 2964-74. 13. Bhatt, A. P.; Bhende, P. M.; Sin, S. H.; Roy, D.; Dittmer, D. P.; Damania, B., Dual inhibition of PI3K and mTOR inhibits autocrine and paracrine proliferative loops in PI3K/Akt/mTOR-addicted lymphomas. Blood 2010, 115, (22), 4455-63. 14. Rosich, L.; Montraveta, A.; Xargay-Torrent, S.; LópeZ-Guerra, M.; Roldán, J.; Aymerich, M.; Salaverria, I.; Beà, S.; Campo, E.; PéreZ-Galán, P.; Roué, G.; Colomer, D., Dual PI3K/mTOR inhibition is required to effectively impair microenvironment survival signals in mantle cell lymphoma. Oncotarget 2014, 5, (16). 15. Furukawa, S.; Wei, L.; Krams, S. M.; Esquivel, C. O.; MartineZ, O. M., PI3Kdelta inhibition augments the efficacy of rapamycin in suppressing proliferation of Epstein-Barr virus (EBV)+ B cell lymphomas. Am J Transplant 2013, 13, (8), 2035-43. 16. Walsh, K.; McKinney, M. S.; Love, C.; Liu, Q.; Fan, A.; Patel, A.; Smith, J.; Beaven, A.; Jima, D. D.; Dave, S. S., PAK1 mediates resistance to PI3K inhibition in lymphomas. Clin Cancer Res 2013, 19, (5), 1106-15. 17. Li, C.; Xin, P.; Xiao, H.; Zheng, Y.; Huang, Y.; Zhu, X., The dual PI3K/mTOR inhibitor NVP-BEZ235 inhibits proliferation and induces apoptosis of burkitt lymphoma cells. Cancer Cell International 2015, 15, (1), 65. 2 18. Zang, C.; Eucker, J.; Liu, H.; Muller, A.; Possinger, K.; ScholZ, C. W., Concurrent inhibition of PI3-kinase and mTOR induces cell death in diffuse large B cell lymphomas, a mechanism involving down regulation of Mcl-1. Cancer letters 2013, 339, (2), 288-97. 19. Rodon, J.; PereZ-Fidalgo, A.; Krop, I. E.; Burris, H.; Guerrero-Zotano, A.; Britten, C. D.; Becerra, C.; Schellens, J.; Richards, D.